1. Field of the Invention
This invention relates generally to a drive shaft of a fan coupling assembly, and more particularly to the means of attachment to the fan drive pulley.
2. Description of the Prior Art
Conventionally, the drive shaft of a fan coupling assembly includes a shaft member upon which a drive rotor of the coupling assembly is fixedly secured, and a flange member for attaching the fan drive pulley thereon. The two members are formed in one piece from a metal rod by cold forging. The metal rod has substantially the same diameter as that of the shaft member. In the conventional method, the diameter of the flange member is required to be three times larger than that of the shaft member, and the thickness of the flange is required to be thicker than is necessary, in order to effectively connect the fan drive pulley therewith. Consequently, the forging process particularly for forming the flange member is so complicated that reduction of the production efficiency has not been avoided, which leads to a high cost of the products.
In addition, if the increase in the drive torque is desired, it is necessary to increase the diameter of the flange member. Due to the problem of the present forging technique in this field, however, it is very difficult to achieve such an increase in diameter.